Those who seek good news about the climate crisis have a place to look for it: the third part of the sixth IPCC Report, the one devoted to mitigation. The Intergovernmental Panel on Climate Change - IPCC is the body created by the United Nations in 1988 to aggregate, summarise and communicate to citizens and political leaders the results of scientific research on climate change. Between 2021 and 2022, the results of the sixth round of the study were published. The first part was released in August and dealt with the physical limits of the Earth - it was very bleak. The second was published in February and concerned the vulnerability of nations and communities: it was defined as "an atlas of human suffering," by United Nations Secretary-General António Guterres. The third part, released on 4 April, is dedicated to mitigation, i.e. the potential for reducing our greenhouse gas emissions into the atmosphere. "It's now or never" is the essence of this part of the Report: we can halve our impact on the atmosphere by the end of the decade, the technologies are there and they are now affordable, able to compete almost anywhere in the world with fossil fuels. Cities, with their transportation and infrastructure, will play a central role in this transition.

Rethink, choose

This was explained in a post by Karen Seto, Yale professor and editor of the section on urban mitigation: "Cities will have 2.5 billion more people by 2050. And many of these cities have not yet been built. The pace of development is very high, but there is so much that can be done." Today, 55 percent of humanity lives in a city; by mid-century, the percentage will be 68 percent. Urban spaces are both cause of and solution for climate change. According to the IPCC Report, the quota of urban emissions grew between 5 and 10 percent between 2015 and 2020 alone. To stop this increase, the key words proposed by the UN are: spatial concentration of people and activities, green infrastructure that is centred on the needs of citizens, reduction of consumption through compact, dense and "walkable" urban models and electrification of transport. As Jim Skea, head of the IPCC Mitigation Working Group, explained, "We see examples of zero-emission buildings in all kinds of climates. It will be necessary to harness all of this mitigation potential in the way we build".

The science is clear: rapid, aggressive measures are needed; the time for incremental change, proceeding in small steps, is over. Existing cities must be rethought, starting with buildings and mobility, and new ones must be imagined with completely different criteria: they must be smaller, they must consume very little, they must be able to enable individual sustainable lifestyles. The IPCC insists very much on this aspect, that of socio-behavioural choices, therefore our personal way of travelling, living and consuming. These choices matter and can reduce emissions by up to 70 percent by mid-century, but climatically appropriate ways of living in a changing world need contexts that make them possible, and the enabling context par excellence is the city.

Spaces, urban policies, electrification

The IPCC model metropolis is on a smaller scale than the sprawling metropolises that are growing in developing countries, and it is criss-crossed by green (plant) and blue (marine or river) infrastructure that can help lower local temperatures and absorb emissions. The effects of nature-based solutions, such as urban forests, would be double: on the one hand, they absorb CO₂, and on the other, they cool homes and streets, reducing the need for air conditioning and thus of energy consumption. The cities of 2050 must be permeated with nature, along the lines of jungle capitals like Singapore, where more than 50 percent of the surface is covered by trees.

New infrastructure planning will be decisive in all areas, according to the IPCC Report. The method is that of integrated spatial planning, to reduce the so-called VMT, vehicle miles travelled, a key indicator in the vision of the IPCC: the travel time that citizens must deal with to meet their needs, starting from work. From this point of view, the turn of many European cities (including Paris and Milan) towards the "fifteen minute" scale is among the solutions considered to be most compatible with climate objectives. In fact, urban growth based on transit reduction can reduce urban emissions by up to 26 percent. Travel must be fully electrified: with existing technologies, the buildings in which people live and the means of transport they use can be transformed at the same time, cutting emissions by the equivalent of 6.9 gigatons of CO₂ by 2030 and the equivalent of 15.3 gigatons of CO2 by 2050. This requires integrated planning and very rapid conversion. What we build today will last for decades: starting an immediate transition saves us the problems of technological lock-in, i.e. being forced to live with obsolete and harmful infrastructure to amortise the costs.

Urban policies must support the citizens' desire for change by reducing distances and should provide an incentive for it, with charges such as congestion pricing or limited traffic zones. Never before has public transportation been presented as a viable, scalable, and cost-effective solution to moving people in a sustainable way as it has been in this IPCC Report. As the demand for mobility continues to grow, energy efficiency is the watchword: the car-centric urban model must be overcome, also because the IPCC stresses how in many metropolises of the world public transport is a sort of vanguard of electrification: where battery-powered buses arrive, electric cars arrive faster. Mitigation is therefore also the promotion of sustainable lifestyles and consumption.

The decisive function of data

Lastly, the essential link for designing a new kind of city is timely monitoring of greenhouse gas emissions, a tool that most contemporary metropolises have yet to equip themselves with. The impact of choices must be measurable with accuracy, so it should be considered as the basis for sustainable development. The new urban emission inventories are one of the areas in which technology is not an imaginary magic bullet to be invoked, but a concrete and practical tool to guide local policies, also so that a reduction in emissions in one sector leading to an increase in another can be avoided. Metropolises of the future need to be thought of as complex living organisms, they require integrated data-driven planning to play their part in reducing emissions, which is a decisive one.

More than half of the world’s population, 55% to be precise, lives in urban areas. This figure was 30% in 1960, and it will be 70% by 2050, according to a forecast in the United Nation’s World Urbanization Prospects 2018 report, frequently mentioned by the media. In the Anthropocene era, and with the world pandemic still in course, the magnetic appeal of the city lives side-by-side with an awareness that the impact of global warming imposes a decisive change of direction in urban development models, or at least the way we have perceived them during the 1900s. We are now aware, with varying degrees of alarmism, that the issues that afflict the ecosystem of the city can impact not only our quality of life but also the very concept of the liveability of the place in which we live. Rising water levels, particulate matter, urban heat islands and the erosion of biodiversity are all threats that we are facing today, and they could become even more of a concern tomorrow. While our everyday life may still seem to maintain that facade of reassurance it had in the past, the debate on solutions that can unite urban development with sustainability continue to advance, involving people and institutions, from international organisations to governments and local communities, on many different levels.

At the same time, other leading-edge solutions aimed at achieving an eventual reconciliation between the size of a construction and the natural order are also gaining ground, with many cities now becoming the trailblazers of virtuous solutions. In this article, we want to tell you the story of three of these cities - Shanghai, Stockholm and Prato – to demonstrate how each one, starting from their specific contexts, size and differing scales, seeks an answer to these problems through innovative projects that could change the lives of each and every one of us in the not too distant future.

Shanghai

We begin our tour in Asia, a continent that has already been affected by climate change, particularly in terms of rising sea levels and the subsequent floods in coastal areas. Between Pakistan, India, Bangladesh, China and Indonesia, there are many cities facing the threat of becoming partially or even completely submerged by the rising oceans. A risk that becomes even more difficult to manage in every high-density urban area along the coast. This is the case in Shanghai, the second largest megalopolis in China, with 25 million inhabitants – according to official figures, but estimated at 30 million if you take into account unofficial residents – which is already in a standoff with these unprecedented ‘high tides’. This immense urban conglomerate is already used to adopting draconian measures to mitigate the impact of pollution. In fact, just ten years ago, the notorious air pollution problem was ‘resolved’ by relocating the entire heavy industry sector 200 kilometres away. Today, in Shanghai, masks and air purifiers have now become the norm, but the concentration of fine dust and the grey mist of smog has significantly plummeted.

However, for several years the principal challenge has been building a barrier to keep out the rising sea waters that surround and transverse the city, also in light of the Yangtze River, one of China’s major water courses. Again, in this case, Shanghai did not opt for half measures. In fact, the Chinese government is building 520 kilometres of anti-flood barriers in Hangzhou Bay, in the southern region of the megalopolis, which also surrounds the islands of Chongming, Hengsha and Changzing. Inspired by a model similar to that of the Mose project in Venice, one of various case studies that was examined when planning this infrastructure, these mobile floodgates have been installed on three dams to help reduce water levels even further, a project based on a case study of the Maeslantkering storm surge barrier in Rotterdam.

Another parameter that has to be evaluated is the incidence of precipitation. Shanghai is not only a mere 3.5 meters above sea level (this varies depending on the area), but it is also hit by two or three typhoons a year. It is from here that the Chinese government has studied a model for the entire country, which is progressively being implemented also in Shanghai: the concept of the ‘Sponge City’. In the face of rising and increasingly intensified rainfall, the urban territory is being made as flood proof as much as possible, i.e. the impermeable tarmac on the city’s surface is being replaced with surfaces that can absorb the stormwaters into the ground. This method not only helps to prevent the flooding of sewers and water channels but also prevents the formation of heat islands in the summer, particularly in areas where there is scarce forestation and the city floor extends over large areas with no space for soil, allowing for a more efficient exchange of humidity.

Prato

From Asia, we return to Europe, more specifically Prato, in Tuscany, a provincial city with an extremely strong identity, tied to the famous local textile industry in its years of economic success as much as in its crisis periods. In this case, it is precisely sustainability that the Tuscan city has courageously chosen as a starting point for its recovery plan: envisaging a low-impact future, capable of driving a new form of social inclusion based around this green vision. With the Prato Urban Jungle project, the city is investing in four pilot sites (three public and one private), transforming them into eco-friendly systems with a high-density of greenery. Through the use of greenified walls and rooftops, collective gardens and replacing concrete with nature, the Prato jungle is transformed into a system that can reduce pollution, favouring a new form of well-being for its citizens.

In the first pilot site, designed by Stefano Boeri Architetti, the company Consiag Estra will find itself with a facade enriched with shrubs, tall trees and climbing plants that will mitigate the impact of the intense surrounding traffic; a move that will also improve the liveability and energy performance of the building. Whereas, in the densely populated residential district of San Giusto, in the social housing area, 1.600 square metres of paving will be transformed into a natural drainage surface, while the facades will be greenified and new gardens will be created, increasing social spaces for the residents. The plans also include a new marketplace that will be built inside a disused warehouse. As well as the greenification of the façade, there will also be constructing a large air factory, based on the botanical filter model developed by Stefano Mancuso. Finally, the shopping centre will be flanked by a high-yield urban greenhouse that will produce zero-mile vegetables, with a restaurant area open to the public. However, this is not a project that came from the upper echelons of government, it was designed together with the citizens through co-planning initiatives, aimed at individualising solutions that are closer to the real needs of the local residents, promote cohesion and maximise the benefits for the parties involved.

Stockholm

The final stage in our journey is Stockholm. Driven by an ambitious plan to become carbon-neutral by 2040, the Swedish capital is experimenting a number of virtuous construction models on its new buildings. These experiments are focused within the Stockholm Royal Seaport area, where they have created 12.000 new habitations and 35.000 offices, all based on the principles of the circular economy, eco-friendly waste management and energy efficiency. The urban development model is centred on inclusivity and gender mainstreaming, facilitating the full participation and liveability of the urban spaces for female residents. Another fast-tracked change is the electrification of the vehicle fleet, which ranges from the introduction of user incentives to the purchase of electric vehicles for both public and privately-owned transport.